Is there temporal variation on solid waste stranding in mangroves ? A case study in Ratones mangrove , Florianopolis , Brazil

Mangrove areas are decreasing around the world due to population increase. The most damaging activities include embankments, shrimp farming, and dumping of wastes. The temporal and spatial stranding patterns of


Introduction
Mangrove forests are very complex, dynamic, highly resilient, and resistant.They are characterized to occur in tropical zones and some subtropical regions all over the world (LUGO; SNEDAKER, 1974;CHAPMAN, 1977;SCHAEFFER-NOVELLI;CIN65*6TRÓN, 1986;SPALDING et al., 1997;LAL, 2003;NAGELKERKEN et al., 2008).Mangrove plant community consists of typical species, which are adapted to high saline substrate and periodical tide flooding (CHAPMAN, 1977;SCHAEFFER-NOVELLI;CINTRÓN, 1986;TOMLINSON, 1988;SPALDING et al., 1997;PARIDA;JHA, 2010).This ecosystem provides breeding, nesting, protection, and feeding to several species (CHAPMAN, 1977;SCHAEFFER-NOVELLI;CINTRÓN, 1986;TOMLINSON, 1988;NAGELKERKEN et al., 2008).Due to its ecological and socioeconomic significance, the Brazilian legislation establishes specific standards to ensure mangroves as permanent preservation areas.However, lack of knowledge about the law among people living nearby mangroves, shortage of resources and staff for environmental inspection agencies, as well as political and economic conflicts constitute strong factors to protection ineffectiveness.
Decrease in mangrove areas around the world is directly related to pressures generated by industrial and urban growth (POLIDORO et al., 2010).Pipeline work, changes in river flows, embankment, shrimp farming, salt extraction, and dumping of wastes are among the most damaging human activities (HAMILTON;SNEDAKER, 1984).The negative impacts of wastes on local fauna includes ingestion (VLIETSTRA; PARGA, 2002;PROVENCHER et al., 2010;TOURINHO et al., 2010;POSSATTO et al., 2011) andentanglement (DERRAIK, 2002), besides dispersion of exotic and invader species (BARNES, 2002;BARNES;MILNER, 2005).Floating anthropogenic objects might facilitate long distance transport of species (THIEL et al., 2011) and result in native diversity loss at new locations (BARNES; MILNER, 2005).
Florianopolis is famous as a tourist city because of its beaches.According to IBGE (2010), this city has 404,224 inhabitants, but it is estimated to increase to almost 1 million during the tourist period.Each month, 766.6 tons of solid wastes are collected with rises to 825.5 tons on summer (COMCAP, 2011).Population explosion on summer without proper infrastructure has tragic consequences for coastal ecosystems.
Although studies about litter on Latin America beaches and the influence of tourism are already well established, they still have to be developed in other marine Is there temporal variation on solid waste stranding?ecosystems (IVAR DO SUL;COSTA, 2007).Researches about urban solid waste in mangroves are very recent and scarce (eg. GREEN;WEBBER, 1996;SOUZA et al., 2008;CORDEIRO;COSTA, 2010;VIEIRA et al., 2011), perhaps because these environments do not have the same aesthetic and economic appeal of beaches (ARAÚJO; COSTA, 2007;IVAR DO SUL;COSTA, 2007;NETO;FONSECA, 2011).Vieira et al. (2011) discuss about solid waste quantities and homogeneity of stranding in Ratones mangrove and show that there were spatial differences on solid waste stranding.Taking into account the expected population variation due to tourism and the proximity of mangrove to crowded beaches, temporal differences are also expected, with more wastes on spring and summer.Therefore, this study aims to analyze temporal variation of solid waste stranding in a mangrove region of Florianopolis city, Brazil.

Material and Methods
Florianopolis is located at Santa Catarina Island (Brazil), nearing the southern boundary of mangrove distribution in South America (CHAPMAN, 1977;SCHAEFFER-NOVELLI;CINTRÓN, 1986;SPALDING et al., 1997).Mangrove forests spread in certain areas both along north and south bays, as well as in island and continent.Some of these mangroves are protected areas, such as the Carijós Ecological Station (Figure 1), which aims to protect Ratones and Saco Grande mangroves.At this region, four 650 m² areas (Figure 1) were chosen (described by VIEIRA et al., 2011) and totally cleaned before the research started, in order to avoid the influence of antecedent debris.Thereafter, two random 50 m² plots were monthly sampled in each area.This study is limited with regard to seasonal analysis, because using months as sampling periods can lead to a seasonal pseudoreplication (HULBERT, 1984) when only one year is taken into account.Nevertheless, temporal variations were focused throughout one year, with samplings between October 2008 and October 2009 during the lowest tide of each month.All solid waste items were analyzed, regardless of being whole or fragmented.These items were removed from samples and given to the company responsible by solid waste management (Companhia de Melhoramentos da Capital -COMCAP) aiming at a correct destination and to avoid interference by double-counting.Quantifying and qualifying processes happened in situ.Debris were not weighted due to their different nature.
Solid waste was categorized as: plastic, nylon, rubber, metal, wood, glass, tissue, ceramic, and other.Data was transformed to log 2 and tested for normal distribution with Shapiro-Wilk test.To test for variance homoscedasticity, Levene's test was used.The temporal variation of solid waste stranding was compared through two-way ANOVA test (α = 0.05) using the software Statistica 7.0 (STATSOFT, 2004) and grouping months into seasons (summer: December to February; autumn: March to May; winter: June to August; and spring: September to November).For significant differences, Tukey test post hoc was applied (ZAR, 1999).Is there temporal variation on solid waste stranding?
When considering the two main types of solid waste (plastic and nylon), the one-way ANOVA test showed a temporal variation for plastic components (F = 3.02; p = 0.03), with higher concentration during summer (Figure 3a).There was also a significant difference between fall and winter (Tukey test; p = 0.05).On the other hand, nylon did not present significant variations between seasons (F = 1.86; p = 0.14) (Figure 3b).
The two-way ANOVA test showed a significant influence of the "area" factor on wastes stranding variation (Table 1).Variation in solid waste stranding according to season showed high standard deviations.The factors "season" and "season with area" presented no difference.But "area" had a significant influence on this variation.These differences indicate that the influence of the factors "area" and "season" are stronger when considered alone than together; it stresses the sampling areas location relevance over temporal changes.Data normality was verified with Shapiro-Wilk test (W = 0.97; p = 0.05) and Levene's test showed the homoscedasticity variation (F = 0.59; p = 0.87).Figure 4 shows the fluctuation in amounts of solid waste strandings during seasons in each area.Areas 1 and 2 had higher amounts in summer, while Area 3 concentrated the stranding on fall.Area 4 had a small and growing variation from spring to winter.Area 2 had fewer wastes and the fact that the confidence interval reaches negative amplitude reflects this very low amount on fall.Variations represent a 95% confidence interval.
There were significant differences in temporal strandings only for plastic.On the other hand, nylon and the wastes total did not have significant temporal variation.These results could be explained by the waste sources dynamics.High values of plastic on summer could be related to population increase because of tourism and its connection to waste production.In the South Atlantic coast, several researches revealed tourist and fishing activities as major causes of marine pollution temporal accumulation (BARNES; MILNER, 2005;IVAR DO SUL;COSTA, 2007;MACHADO;FILLMANN, 2010;WIDMER;HENNEMANN, 2010;CARVALHO-SOUZA;TINÔCO, 2011;NETO;FONSECA, 2011;PORTZ et al., 2011;TOURINHO;FILMANN, 2011;VIEIRA et al., 2011).
Highest stranding in Areas 1 and 2 can be due to direct exposition to marine currents (VIEIRA et al., 2011).Area 2 had fewer residues, possibly because of Spartina alterniflora Loisel (Poaceae) effect (VIEIRA et al., 2011).Locations with Spartina alterniflora Loisel (Poaceae) dense edges in front seem to have less solid waste inside the mangrove forest, perhaps because this grass formation acts as a mesh barrier.Negative amplitude of confidence intervals in Area 2 may reflect low stranding in three seasons at this area.Vieira et al. (2011) found out the existence of spatial patterns in solid waste stranding distribution; however, this study reports the lack of a well established temporal variation.
During winter, windy and rainy weather in days previous to data collection may have contributed to light weight materials stranding, such as plastics.Wind and rain in days previous to data collection during summer and spring were also observed, thus contributing to solid waste presence in areas exposed to marine currents (Areas 1 and 2).
The main concern arising from this information is that solid waste stranding is occurring throughout the year in the whole region.Most wastes consist of synthetic products which are difficult to be degraded in the natural environment.Solid waste stranding can affect fish oviposition in grass (Spartina spp.) and pneumatophores.Human wastes cause significant threats to the marine ecosystem, representing danger not only to the biota, but also to social activities and people's health (OIGMAN-PSZCZOL;CREED, 2007;NETO;FONSECA, 2011).
Seasonal variation scenarios with regard to solid waste stranding need continued studies, with comparison between different years (e.g.NETO;FONSECA, 2011;PORTZ et al., 2011;SANTANA-NETO et al., 2011).We also emphasize the variations found in sites close to urbanized areas (Areas 1 and 3) and the transitional Is there temporal variation on solid waste stranding?effect between ecosystems (Area 4), according to discussions of Vieira et al. (2011).Constant educational projects involving communities and tourists that use the region are mandatory, as well as actions towards impacts related to intense urbanization mitigation, such as goods consumption, with consequent waste production and illegal waste dump.

FIGURE 2 :
FIGURE 2: Percentage of solid waste during seasons between 2008 and 2009 at the Ratones mangrove, Brazil.

FIGURE 3 :
FIGURE 3: Average of solid waste stranded for plastic (a) and nylon (b) components throughout the seasons at the Ratones mangrove, Brazil.Boxes correspond to standard deviation, bars to confidence interval of 95% and black dots are outliers.

FIGURE 4 :
FIGURE 4: Fluctuation in solid waste stranding during seasons at four studied areas, Ratones mangrove (Brazil).Variations represent a 95% confidence interval.

TABLE 1 :
Results from two-way ANOVA testing season and area influence on debris stranding at the Ratones mangrove, Santa Catarina Island (Brazil).